ABSTRACT
BACKGROUND: G protein-coupled receptor, family C, group 5 (GPRC5B), a retinoic acid-inducible orphan G-protein-coupled receptor (GPCR), is a member of the group C metabotropic glutamate receptor family proteins presumably related in non-canonical Wnt signaling. In this study, we investigated altered GPRC5B expression in the dorsal horn of the spinal cord after spinal nerve injury and its involvement in the development of neuropathic pain. METHODS: After induction of anesthesia by intraperitoneal injection of pentobarbital (35 mg /kg), the left L5 spinal nerve at the level of 2 mm distal to the L5 DRG was tightly ligated with silk and cut just distal to the ligature. Seven days after nerve injury, animals were perfused with 4% paraformaldehyde, and the spinal cords were extracted and post-fixed at 4degrees C overnight. To identify the expression of GPRC5B and analyze the involvement of GPRC5B in neuropathic pain, immunofluorescence was performed using several markers for neurons and glial cells in spinal cord tissue. RESULTS: After L5 spinal nerve ligation (SNL), the expression of GPRC5B was decreased in the ipsilateral part, as compared to the contralateral part, of the spinal dorsal horn. SNL induced the downregulation of GPRC5B in NeuN-positive neurons in the spinal dorsal horn. However, CNPase-positive oligodendrocytes, OX42-positive microglia, and GFAP-positive astrocytes were not immunolabeled with GPRC5B antibody in the spinal dorsal horn. CONCLUSIONS: These results imply that L5 SNL-induced GPRC5B downregulation may affect microglial activation in the spinal dorsal horn and be involved in neuropathic pain.
Subject(s)
Animals , Child , Humans , Anesthesia , Astrocytes , Child, Orphaned , Diagnosis-Related Groups , Down-Regulation , Fluorescent Antibody Technique , Horns , Injections, Intraperitoneal , Ligation , Microglia , Neuralgia , Neuroglia , Neurons , Oligodendroglia , Pentobarbital , Receptors, Metabotropic Glutamate , Silk , Spinal Cord , Spinal NervesABSTRACT
BACKGROUND: Upregulation of one type of the pro-inflammatory chemokine (CCL2) and its receptor (CCR2) following peripheral nerve injury contributes to the induction of neuropathic pain. Here, we examined whether another type of chemokine (CCL3) is involved in neuropathic pain. METHODS: We measured changes in mechanical and thermal sensitivity in the hind paws of naive rats or rats with an L5 spinal nerve ligation (SNL) after intra-plantar injection of CCL3 or met-RANTES, an antagonist of the CCL3 receptor, CCR1. We also measured CCL3 levels in the sciatic nerve and the hind paw skin as well as CCR1 expression in dorsal root ganglion (DRG) cells from the lumbar spinal segments. RESULTS: Intra-plantar injection of CCL3 into the hind paw of naive rats mimicked L5 SNL-produced hyperalgesia. Intra-plantar injection of met-RANTES into the hind paw of rats with L5 SNL attenuated hyperalgesia. L5 SNL increased CCL3 levels in the sciatic nerve and the hind paw skin on the affected side. The number of CCR1-positive DRG cells in the lumbar segments was not changed following L5 SNL. CONCLUSIONS: Partial peripheral nerve injury increases local CCL3 levels along the degenerating axons during Wallerian degeneration. This CCL3 binds to its receptor, CCR1, located on adjacent uninjured afferents, presumably nociceptors, to induce hyperalgesia in the neuropathic pain state.
Subject(s)
Animals , Rats , Axons , Chemokine CCL3 , Chemokine CCL5 , Diagnosis-Related Groups , Ganglia, Spinal , Hyperalgesia , Ligation , Neuralgia , Nociceptors , Peripheral Nerve Injuries , Peripheral Nerves , Receptors, CCR1 , Sciatic Nerve , Skin , Spinal Nerves , Up-Regulation , Wallerian DegenerationABSTRACT
PURPOSE: To determine the relationship between change in the expression of the p75 neurotrophin receptor (NTR) and transient receptor potential vanilloid 1 (TRPV1) after a spinal nerve injury with time. MATERIALS AND METHODS: The L5 and L6 spinal nerve of the rats were cut unilaterally. The spinal cord and dorsal root ganglion (DRG) were subjected to immunohistochemistry for p75 NTR and TRPV1. RESULTS: The immunoreaction (IR) for p75 NTR in the neuronal cytoplasm was persistently lower on the ipsilateral L5 and L6 DRG but higher in the satellite cells and fibers. The colocalization between p75 NTR and TRPV1 was increased temporarily in the L4 DRG in both sides. In the spinal cord, p75 NTR-IR decreased temporalily in the ipsilateral dorsal horn of the L4-L6 level and had recovered at 28 days after injury. CONCLUSION: These results show that a differential change in the expression of p75 NTR and TRPV1 is related to the different functional recovery of the sensory and motor system, and that increased colocalizations between p75 NTR and TRPV1 in a non-injured DRG might be related to the development of neuropathic pain after a peripheral nerve injury.
Subject(s)
Animals , Rats , Cytoplasm , Diagnosis-Related Groups , Ganglia, Spinal , Horns , Immunohistochemistry , Neuralgia , Neurons , Peripheral Nerve Injuries , Receptor, Nerve Growth Factor , Spinal Cord , Spinal Nerve Roots , Spinal NervesABSTRACT
PURPOSE: The authors studied the effect of the 3-AB, an inhibitor of poly(ADP-ribose)polymerase (PARP), on the changes of primary afferents and spinal cord after spinal nerve injury. METHOD: The L5 and L6 spinal nerve of the rats were cut, and 3-AB (10 mg/Kg) was injected intraperitoneally once per day. The animals were sacrificed 3 days, 7 days, 14 days and 28 days after nerve injury. Binding of isolectin B4 (IB4) and immunohistochemistry (IHC) of CGRP for the changes in primary afferents, IHC of NK1 for sensory neurons, and of cleaved caspase 3 and NeuN for the apoptotic changes in spinal neurons were performed. RESULT: Decreased binding of IB4 and immunoreactivity (IR) for CGRP, increase of IR for NK1, and cleaved caspase 3 in both neurons and glia in ipsilateral dorsal horn were observed after spinal nerve injury. These changes were attenuated, especially at between 3 days and 14 days, by administration of 3-AB. CONCLUSION: It is suggested that inhibition of PARP by 3-AB may attenuate alterations of primary afferents and spinal neurons, at least in early stage, after spinal nerve injury.
Subject(s)
Animals , Rats , Apoptosis , Caspase 3 , Horns , Immunohistochemistry , Lectins , Neuroglia , Neurons , Sensory Receptor Cells , Spinal Cord , Spinal NervesABSTRACT
PURPOSE: The authors studied the effect of the 3-AB, an inhibitor of poly(ADP-ribose)polymerase (PARP), on the changes of primary afferents and spinal cord after spinal nerve injury. METHOD: The L5 and L6 spinal nerve of the rats were cut, and 3-AB (10 mg/Kg) was injected intraperitoneally once per day. The animals were sacrificed 3 days, 7 days, 14 days and 28 days after nerve injury. Binding of isolectin B4 (IB4) and immunohistochemistry (IHC) of CGRP for the changes in primary afferents, IHC of NK1 for sensory neurons, and of cleaved caspase 3 and NeuN for the apoptotic changes in spinal neurons were performed. RESULT: Decreased binding of IB4 and immunoreactivity (IR) for CGRP, increase of IR for NK1, and cleaved caspase 3 in both neurons and glia in ipsilateral dorsal horn were observed after spinal nerve injury. These changes were attenuated, especially at between 3 days and 14 days, by administration of 3-AB. CONCLUSION: It is suggested that inhibition of PARP by 3-AB may attenuate alterations of primary afferents and spinal neurons, at least in early stage, after spinal nerve injury.